Optical induction of muscle contraction at the tissue scale through intrinsic cellular amplifiers

Brain capillary pericytes exert a substantial but slow influence on blood flow

The majority of the brain's vasculature is composed of intricate capillary networks lined by capillary pericytes. However, it remains unclear whether capillary pericytes influence blood flow. Using two-photon microscopy to observe and manipulate brain capillary pericytes in vivo, we find that their optogenetic stimulation decreases lumen diameter and blood flow, but with slower kinetics than similar stimulation of mural cells on upstream pial and precapillary arterioles. This slow vasoconstriction was inhibited by the clinically used vasodilator fasudil, a Rho-kinase inhibitor that blocks contractile machinery. Capillary pericytes were also slower to constrict back to baseline following hypercapnia-induced dilation, and slower to dilate towards baseline following optogenetically induced vasoconstriction. Optical ablation of single capillary pericytes led to sustained local dilation and a doubling of blood cell flux selectively in capillaries lacking pericyte contact. These data indicate that capillary pericytes contribute to basal blood flow resistance and slow modulation of blood flow throughout the brain.

Femtosecond laser pulse assisted photoporation for drug delivery in Chronic myelogenous leukemia cells

Chronic myelogenous leukemia (CML) is a myeloproliferative disorder occurs in the pluripotent hematopoietic stem cell. Currently, first-generation tyrosine kinase inhibitor (TKI) imatinib is the mainstay for the treatment of CML. Second generation TKI's like ponatinib, dasatinib, nilotinib, and bafetinib were treated against resistant CML. However, several CML patients develop resistance towards all existing inhibitors. Curcumin (Curcuma longa) a plant-derived natural compound is an effective bioactive component against various cancers including CML. Many studies have shown that curcumin induces time- and dose-dependent apoptosis in CML cells by regulating various downstream molecular regulators. Despite curcumin's selective cytotoxicity towards cancer cells, it has very poor bioavailability both in in-vitro and in-vivo conditions. In this present study, we have used femtosecond laser (fs-laser) pulses to ablate the cell membrane and standardized the conditions required for creating a cell membrane pores with less lethality. Following fs-laser pulse irradiation, K562 cells were incubated along with curcumin 30 μM for 0 h, 6 h,12 h and 24 h. Interestingly irradiated cells have shown higher sensitivity towards curcumin than non-irradiated cells. Immunoblotting studies showed higher induction levels of cleaved caspase 3 and 9 in irradiated population than non-irradiated. In summary, the results prove that irradiation by fs-laser pulses enhanced the bioavailability of curcumin and shows caspase-mediated cell death in irradiated CML cells than other populations.

Induction of neuronal activation by femtosecond-pulsed laser irradiation and its potential application for amyloid-β-induced toxicity assessment

Manipulating neural activity is crucial for studying the neural connectivity and the pathophysiology of neurodegenerative disease. Among various techniques for neural activation, direct optical stimulation method with femtosecond-pulsed laser is simple and can be specifically applied on a single neuron. Brief irradiation of femtosecond laser pulses on a neuron elevates intracellular calcium, and it propagates to adjacent neurons. However, the mechanisms of laser-induced neural activation are still unclear. In this report, we have elucidated the mechanism of laser-induced neural activation which could be mediated by superoxide, specifically blocked by diphenyleneiodonium chloride, and depletion in intracellular calcium storage. Furthermore, we also showed that the propagation of calcium initiated by laser stimulation is dependent on the presence of extracellular calcium as well as electrical and chemical synapses. We verified the applicability of such mechanism for the assessment of neuronal functionality, by measuring calcium elevation, intracellular calcium propagation, ROS increase, and performing cell death assay in vehicle and Aβ-treated neurons. This work suggests promising applications of the potential for implementing such laser-induced neural activation for rapid and reliable drug screening.

Cytosolic irradiation of femtosecond laser induces mitochondria-dependent apoptosis-like cell death via intrinsic reactive oxygen cascades

High-intensity femtosecond lasers have recently been used to irreversibly disrupt nanoscale structures, such as intracellular organelles, and to modify biological functions in a reversible manner: so-called nanosurgery and biophotomodulation. Femtosecond laser pulses above the threshold intensity sufficient for reversible biophotomodulation can cause irreversible changes in the irradiated cell, eventually leading to cell death. Here, we demonstrated that cytosolic irradiation with a femtosecond laser produced intrinsic cascades of reactive oxygen species (ROS), which led to rapid apoptosis-like cell death via a caspase and poly (ADP-ribose) polymerase 1 (PARP-1) signaling pathway. We further showed that cells with enhanced mitochondrial fusion activity are more resilient to laser-induced stress compared to those with enforced mitochondrial fission. Taken together, these findings provide fundamental insight into how optical stimulation intervenes in intrinsic cellular signaling pathways and functions.